| 题名 | 三相萃取传质机理与过程强化 |
| 作者 | 于品华 |
| 学位类别 | 博士 |
| 答辩日期 | 2012-06-03 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 刘会洲 |
| 关键词 | 三相萃取 相体积 分配率 微相传质 过程强化 |
| 其他题名 | Mass Transfer Mechanism in Three-Liquid-Phase Extraction and Process Intensification |
| 学位专业 | 化学工艺 |
| 中文摘要 | 由有机溶剂-水溶性聚合物-盐水构成的液液液三相体系是一种基于界面现象的微乳相萃取技术。该技术利用的是新相的生成及相间物化性质的差异来实现不同溶质的差别分配，同时三相体系的相行为受聚合物-盐双水相的成相行为影响较大。开展三相体系成相行为与传质行为关联、微相传质过程的研究对实现溶质分配的控制和过程强化具有重要意义。本文在详细考察聚合物双水相及三相相体积变化的基础上，研究了模拟溶质在这两个体系中的分配行为与相行为之间的联系，建立了微相传质模型，探讨了溶质分配机理，实现了过程强化。主要研究内容包括：成相组分类型及浓度对双水相及三相体积的影响规律。酸度升高导致双水相分相所需盐量增加，(NH4)2SO4的缓冲盐性质是引起相体积发生改变的根本原因；成相盐的盐析能力及其同聚合物的相互作用是影响双水相和三相体积变化的重要因素，盐浓度升高引起聚合物链脱水，造成聚合物相体积减小；较高分子量的PEG (聚乙二醇)或疏水PPO(聚丙二醇)链段的引入引起聚合物相体积减小；聚合物和有机溶剂之间的Hoy溶解度参数差异是引起三相体积改变主要原因。成相组分的类型对三相传质分配的影响及其与相体积变化的关系。成相盐阴阳离子的性质对溶质的传质分配影响较大，双水相传质不仅与聚合物相的物化性质有关，而且与溶质本身的性质有关；聚合物分子量增大或疏水链段的引入导致在聚合物相Ph (苯酚)/ o-NP (邻硝基苯酚)的分配率上升、Pt(IV)/Pd(II)/Rh(III)的分配率下降；聚合物分子结构的差异引起聚合物相体积的变化，带来主体相物化性质的改变，最终导致溶质传质行为的改变；有机溶剂的供电子能力和疏水性是溶质从聚合物相向有机相传质的驱动力；三相传质过程首先是溶质与聚合物以疏水或静电作用力结合传质进入聚合物中相，加入有机溶剂后，进一步传质进入有机上相。成相组分的浓度对三相传质分配的影响及其与相体积变化的关系。酸度变化造成SO42-在水中离子形态的转变而盐浓度则影响PEG或EOPO(聚氧乙烯-聚氧丙烯无规共聚物)分子的水化状态，二者均造成聚合物相体积及其物化性质的改变，最终影响溶质的传质分配行为；聚合物浓度的升高导致聚合物相体积的膨胀，造成其萃取容量及聚合物-盐水相浓度梯度的增大，导致溶质分配率的增大；有机溶剂加入量的增大引起有机相萃取容量及上中相浓度梯度的增大，从而有利于溶质从聚合物相向有机相传质。溶质分配系数的Diamond-Hsu模型关联、体积参数相关的分配系数预测模型的建立。对于Ph/o-NP/p-NP(对硝基酚)，Diamond-Hsu模型的二次拟合曲线与数据的关联结果令人满意，而改进的Diamond-Hsu模型的三次方程较好的关联了Pt(IV)/Pd(II)/Rh(III)的分配系数；证实了Ph/o-NP/p-NP与聚合物的主要作用力为疏水作用，而静电作用力对Pt(IV)/Pd(II)/Rh(III)的分配贡献较大；Ph/o-NP/p-NP的分配系数lnK与体积参数R的二次多项式拟合方程与实验数据符合较好，而Pt(IV)/Pd(II)则服从双曲线方程，Rh(III)为指数方程；lnK-R的关联结果证实了在聚合物体积即R变化过程中，聚合物相物化性质的演变对传质分配的贡献。溶质分配的微相传质模型的建立。PEG或EOPO受聚合物浓度、盐度或pH影响在聚集过程中电导、水含量不断变化，其物化性质如疏水性、活性位点数目的改变最终导致溶质传质行为的变化；盐析聚合物相与平衡水相均存在明显的聚集体特征且尺寸随盐度不断变化；提出了溶质分配的微相传质模型，认为在宏观相分离前，水溶液中存在聚合物微相，而溶质被聚合物微相所捕集，伴随着宏观相分离，溶质随之完成了双水相的传质分配，加入有机溶剂后，溶质再次实现从聚合物相向有机相的传质；提出了以静电力为主的Pt(IV)/Pd(II)/Rh(III)的微相界面传质模型，认为阳离子如Na+与PEO(聚氧乙烯)上氧原子反应生成准阳离子，周围富集的阴离子如SO42-、Cl-与三种金属的氯配阴离子通过阴离子交换进行传质。气助三相溶剂萃取技术的提出及气助三相萃取设备的开发。气助三相萃取过程能够实现聚合物微相与有机溶剂的捕集，减少萃取剂在水相的分散损失，提高并强化萃取效率；对包含p-NP和o-NP的模拟体系，气助三相萃取过程中p-NP/o-NP在相间的分配比、富集因子与常规三相萃取相比均有较大幅度的提高；高气速及多段布气气助三相萃取设备的开发不仅可以实现在高气速下上中相的传质强化，而且有助于分相。 |
| 英文摘要 | Three-liquid-phase system (TLPS) composed of organic solvent-water soluble polymer-brine is a kind of microemulsion extraction technique based on the interfacial phenomena. The unevenly partitioning of target solutes is realized based on the new phases’ formation and the differences in physicochemical properties between the phases, whereas the phase behavior of TLPS is subjected to the phase-forming behavior of polymer-salt aqueous two-phase system (ATPS). The investigation of the interrelationship between the phase behavior of TLPS and the partition behavior of solutes, microphase mass transfer process is important to realize the control of the distribution of objectives and process intensification. In this dissertation, the parameters that affect phase behavior of polymer based ATPS and TLPS were investigated in detail and the relationship between the phase behavior and distribution of model solutes in these two systems was also studied. Finally, the microphase mass transfer model was established. The partitioning mechanism of solutes has been also discussed and the process intensification was achieved. The main research contents include: The influence of the type of phase-forming components and their concentrations on the phase volume of ATPS as well as TLPS. Increase in H+ concentration resulted in the increase in the amount of salt required at the phase separation point of ATPS. The buffer properties of (NH4)2SO4 is the origin of phase evolution. The salting-out ability of phase-forming salt and interaction between salt and polymers could account for the change in phase volume of ATPS and TLPS. Elevation of salt concentration contributed to the dehydration of polymer chain, and therefore volume of polymer phase shrinked. PEG with higher molecular weight or introduction of hydrophobic PPO segment led to decreased volume of salting-out polymer phase. The difference in hoy solubility parameter (δtot) between polymer and organic solvent was the main reason for the variation in phase volume of TLPS. Influence of the type of phase-forming components on three-liquid-phase mass transfer and its relationship with phase volume change. The properties of salt anions and cations affected the mass transfer and distribution of solutes remarkably. Mass transfer in ATPS was not only related to the change in physicochemical properties of polymer phase, but to the properties of solutes. Increased molecular weight of polymer or introduction of hydrophobic segment resulted in the climbing up in distribution of Ph/o-NP, and dropping down in that of Pt(IV)/Pd(II)/Rh(III). Difference in the molecular structure of polymer contributed to the change in volume of polymer phase, resulting in the variation in physicochemical properties of body phase and finally the change in mass transfer of solutes. The hydrophobicity and electron-donating ability of organic solvent were the driving forces for the mass transfer of solutes from polymer phase to the organic phase. Mass transfer profile in TLPS could be described as the firstly transfer of solutes from aqueous to polymer phase via hydrophobic or electrostatic interaction, then further from polymer phase into organic phase after the addition of organic solvent. Influence of the concentration of phase-forming components on three-liquid-phase mass transfer and its relationship with phase volume change. Change in acidity promoted the transformation of the ionic form of SO42- in aqueous solution while salt concentration affected the hydration state of PEG or EOPO molecules, both of which brought about the variation in volume of polymer phase and its physicochemical properties, finally leading to the change in mass transfer in ATPS. Increase in polymer concentration caused the swelling of polymer phase and elevated concentration gradient of solutes between polymer and salt aqueous phases, creating the increase in distributions. Increase in organic solvent concentration also contributed to the expanded extraction capacity of organic phase and elevated concentration gradient between polymer and organic phases, therefore facilitating the mass transfer of solutes from middle to top phases of TLPS. The correlation of distribution coefficient based on Diamond-Hsu model and the establishment of prediction model for partition coefficients related to phase volumes. Regarding Ph/o-NP/p-NP, the correlation results of second order fitting curve with the experimental data based on Diamond-Hsu model was satisfying, whereas the three order fitting curve based on the modified Diamond-Hsu equation correlated well with the distribution coefficients of Pt(IV)/Pd(II)/Rh(III). It was confirmed hydrophobic interaction was the main interaction terms between Ph/o-NP/p-NP and polymer, whereas electrostatic interaction contributed more to the distribution of Pt(IV)/Pd(II)/Rh(III). The second order polynomial equation between the distribution coefficient lnK and R for Ph/o-NP/p-NP correlated well with experimental data, while the relationship between lnK and R for Pt(IV)/Pd(II) observed the hyperbolic equation. As for Rh(III), exponential equation was more appropriate. Correlation equations between lnK and R verified contribution of the evolution in physicochemcal properties of polymer phase to the mass transfer process during the change in R related to phase volume. Establishment of the microphase mass transfer model for the distribution of solutes. Electrical conductivity, water content underwent continuous change during the aggregation of PEG or EOPO induced by polymer or salt concentrations and pH. The alteration in physicochemical properties of polymer phase e.g. hydrophobicity, number of activity sites led to different distribution behavior. Typical clustering characteristics were observed in PEG or EOPO phase as well as equilibrious salt aqueous phase, and the size of clusters underwent continuous change versus salt concentration. Microphase mass transfer model was proposed, believing polymer microphase did exist in aqueous solution before apparent phase separation, when target solutes were trapped by polymer microphase. Accompanying apparent phase separation, mass transfer in ATPS then completed. After the addition of organic solvent, the solutes then further transferred from polymer phase to organic phase. A microphase interfacial mass transfer model with electrostatic interaction as driving force for the distribution of Pt(IV)/Pd(II)/Rh(III) was proposed, considering cations e.g. Na+ interacted with –O– in PEO to form pseudopolycations, in which vicinity anions of SO42- or Cl- could be substituted by chloro-anions of Pt(IV)/Pd(II)/Rh(III) through anion exchange mechansim. The proposition of gas-assisted three-liquid-phase extraction (GATE) and development of GATE apparatus. GATE could realize the collection of polymer microphase and organic solvent, thus reduce the loss of extractant dispersed in aqueous solution and improve extraction efficiency. Regarding to model system containing p-NP and o-NP, the distribution ratio and concentration factor between the phases were enhanced significantly compared with that in conventional TLPS. The development of GATE equipment under high gas velocity or multi-stage sparging could not only intensify the mass transfer rate between the top and middle phases under high gas flow rate, but also contributed to phase separation. |
| 语种 | 中文 |
| 公开日期 | 2013-09-25 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1793]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 于品华. 三相萃取传质机理与过程强化[D]. 中国科学院研究生院. 2012. |
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